fix value set validation for primitive types when an expansion is provided, and the code system is not known

org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/terminologies/ValueSetCheckerSimple.java

@@ -164,6 +164,9 @@ public class ValueSetCheckerSimple implements ValueSetChecker {
           throw new FHIRException("Unable to evaluate based on empty code system");
         }
         res = validateCode(code, cs);
+      } else if (cs == null && valueset.hasExpansion() && inExpansion) {
+        // we just take the value set as face value then
+        res = new ValidationResult(IssueSeverity.INFORMATION, null);
       } else {
         // well, we didn't find a code system - try the expansion? 
         // disabled waiting for discussion